C#中利用DPAPI加密解密數據

加密解密的一個函數

 

using System;
using System.Runtime.InteropServices;
using System.Text;
using System.Security;

namespace CryptProtection
...{
    [Serializable()]
    public sealed class DataProtection
    ...{
        [Flags()]
        public enum CryptProtectPromptFlags
        ...{
            CRYPTPROTECT_PROMPT_ON_UNPROTECT = 0x01,
            CRYPTPROTECT_PROMPT_ON_PROTECT = 0x02,
            CRYPTPROTECT_PROMPT_RESERVED = 0x04,
            CRYPTPROTECT_PROMPT_STRONG = 0x08,
            CRYPTPROTECT_PROMPT_REQUIRE_STRONG = 0x10
        }

        [Flags()]
        public enum CryptProtectDataFlags
        ...{
            CRYPTPROTECT_UI_FORBIDDEN = 0x01,
            CRYPTPROTECT_LOCAL_MACHINE = 0x04,
            CRYPTPROTECT_CRED_SYNC = 0x08,
            CRYPTPROTECT_AUDIT = 0x10,
            CRYPTPROTECT_NO_RECOVERY = 0x20,
            CRYPTPROTECT_VERIFY_PROTECTION = 0x40,
            CRYPTPROTECT_CRED_REGENERATE = 0x80
        }

        加密數據#region 加密數據
        public static string ProtectData(string data, string name)
        ...{
            return ProtectData(data, name, 
                CryptProtectDataFlags.CRYPTPROTECT_UI_FORBIDDEN | CryptProtectDataFlags.CRYPTPROTECT_LOCAL_MACHINE);
        }

        public static byte[] ProtectData(byte[] data, string name)
        ...{
            return ProtectData(data, name, 
                CryptProtectDataFlags.CRYPTPROTECT_UI_FORBIDDEN | CryptProtectDataFlags.CRYPTPROTECT_LOCAL_MACHINE);
        }

        public static string ProtectData(string data, string name, CryptProtectDataFlags flags)
        ...{
            byte[] dataIn = Encoding.Unicode.GetBytes(data);
            byte[] dataOut = ProtectData(dataIn, name, flags);

            if (dataOut != null)
                return (Convert.ToBase64String(dataOut));
            else
                return null;
        }

        /**//// <summary>
        /// 加密數據
        /// </summary>
        /// <param name="data">要加密的明文數據</param>
        /// <param name="name">有意義的描述，此描述會加到加密後的數據中</param>
        /// <param name="dwFlags">flags的位標誌</param>
        /// <returns></returns>
        private static byte[] ProtectData(byte[] data, string name, CryptProtectDataFlags dwFlags)
        ...{
            byte[] cipherText = null;

            // copy data into unmanaged memory
            //DATA_BLOB結構，用於CryptProtectData參數
            DPAPI.DATA_BLOB din = new DPAPI.DATA_BLOB();
            din.cbData = data.Length;

            //Marshal類的作用：提供了一個方法集，這些方法用於分配非託管內存、複製非託管內存塊、將託管類型轉換爲非託管類型，
            //此外還提供了在與非託管代碼交互時使用的其他雜項方法。 
            //爲din.pbData分配內存
            din.pbData = Marshal.AllocHGlobal(din.cbData);

            //InPtr結構:用於表示指針或句柄的平臺特定類型
            //分配內存錯誤，拋出內存不足異常
            //IntPtr.Zero:一個只讀字段，代表已初始化爲零的指針或句柄
            if (din.pbData.Equals(IntPtr.Zero))
                throw new OutOfMemoryException("Unable to allocate memory for buffer.");

            //將data數組中的數據複製到pbData內存指針中
            Marshal.Copy(data, 0, din.pbData, din.cbData);

            //聲明DPAPI類的DATA_BLOB公共結構類型
            DPAPI.DATA_BLOB dout = new DPAPI.DATA_BLOB();

            try
            ...{
                //加密數據
                bool cryptoRetval = DPAPI.CryptProtectData(ref din, name, IntPtr.Zero, IntPtr.Zero, IntPtr.Zero, dwFlags, ref dout);

                //判斷加密是否成功
                if (cryptoRetval) // 成功
                ...{
                    int startIndex = 0;
                    //分配cipherText數據元素大小爲dout.cbData
                    cipherText = new byte[dout.cbData];
                    //從dout.pbData內存指針指向的內容拷貝到byte數組cipherText中
                    Marshal.Copy(dout.pbData, cipherText, startIndex, dout.cbData);
                    //從內存中釋放指針指向的數據I
                    DPAPI.LocalFree(dout.pbData);
                }
                else
                ...{
                    //加密失敗，獲得錯誤信息
                    int errCode = Marshal.GetLastWin32Error();
                    StringBuilder buffer = new StringBuilder(256);
                    //顯示錯誤信息
                    Win32Error.FormatMessage(Win32Error.FormatMessageFlags.FORMAT_MESSAGE_FROM_SYSTEM, IntPtr.Zero, errCode, 0, buffer, buffer.Capacity, IntPtr.Zero);
                }
            }
            finally
            ...{
                // 如果din.pbData非空，則釋放din.pbData使用的內存
                if (!din.pbData.Equals(IntPtr.Zero))
                    Marshal.FreeHGlobal(din.pbData);
            }

            //返回加密後的數據
            return cipherText;
        }
        #endregion


        解密數據#region 解密數據
        public static byte[] UnprotectData(byte[] data)
        ...{
            return UnprotectData(data, CryptProtectDataFlags.CRYPTPROTECT_UI_FORBIDDEN);
        }

        public static string UnprotectData(string data)
        ...{
            byte[] dataIn = Convert.FromBase64String(data);
            byte[] dataOut = UnprotectData(dataIn);

            if (dataOut != null)
                return Encoding.Unicode.GetString(dataOut);
            else
                return null;
        }

        internal static byte[] UnprotectData(byte[] data, CryptProtectDataFlags dwFlags)
        ...{
            byte[] clearText = null;

            // copy data into unmanaged memory
            DPAPI.DATA_BLOB din = new DPAPI.DATA_BLOB();
            din.cbData = data.Length;
            din.pbData = Marshal.AllocHGlobal(din.cbData);

            if (din.pbData.Equals(IntPtr.Zero))
                throw new OutOfMemoryException("Unable to allocate memory for buffer.");

            Marshal.Copy(data, 0, din.pbData, din.cbData);

            DPAPI.DATA_BLOB dout = new DPAPI.DATA_BLOB();

            try
            ...{
                bool cryptoRetval = DPAPI.CryptUnprotectData(ref din, null, IntPtr.Zero, IntPtr.Zero, IntPtr.Zero, dwFlags, ref dout);

                if (cryptoRetval) // ERROR_SUCCESS?
                ...{
                    clearText = new byte[dout.cbData];
                    Marshal.Copy(dout.pbData, clearText, 0, dout.cbData);
                    DPAPI.LocalFree(dout.pbData);
                }
                else
                ...{
                    int errCode = Marshal.GetLastWin32Error();
                    StringBuilder buffer = new StringBuilder(256);
                    Win32Error.FormatMessage(Win32Error.FormatMessageFlags.FORMAT_MESSAGE_FROM_SYSTEM, IntPtr.Zero, errCode, 0, buffer, buffer.Capacity, IntPtr.Zero);
                }
            }
            finally
            ...{
                // free the allocated memory in use
                if (!din.pbData.Equals(IntPtr.Zero))
                    Marshal.FreeHGlobal(din.pbData);
            }

            return clearText;
        }
        #endregion

        internal static void InitPromptstruct(ref DPAPI.CRYPTPROTECT_PROMPTSTRUCT ps)
        ...{
            ps.cbSize = Marshal.SizeOf(typeof(DPAPI.CRYPTPROTECT_PROMPTSTRUCT));
            ps.dwPromptFlags = 0;
            ps.hwndApp = IntPtr.Zero;
            ps.szPrompt = null;
        }
    }

    //允許託管代碼不經過堆棧步即調入非託管代碼
    [SuppressUnmanagedCodeSecurityAttribute()]
    internal class DPAPI
    ...{
        [DllImport("crypt32")]
        public static extern bool CryptProtectData(ref DATA_BLOB dataIn, string szDataDescr, IntPtr optionalEntropy, IntPtr pvReserved,
            IntPtr pPromptStruct, DataProtection.CryptProtectDataFlags dwFlags, ref DATA_BLOB pDataOut);

        [DllImport("crypt32")]
        public static extern bool CryptUnprotectData(ref DATA_BLOB dataIn, StringBuilder ppszDataDescr, IntPtr optionalEntropy,
            IntPtr pvReserved, IntPtr pPromptStruct, DataProtection.CryptProtectDataFlags dwFlags, ref DATA_BLOB pDataOut);

        [DllImport("Kernel32.dll")]
        public static extern IntPtr LocalFree(IntPtr hMem);

        [StructLayout(LayoutKind.Sequential)]
            public struct DATA_BLOB
        ...{
            public int cbData;
            public IntPtr pbData;
        }

        [StructLayout(LayoutKind.Sequential)]
            public struct CRYPTPROTECT_PROMPTSTRUCT
        ...{
            public int cbSize; // = Marshal.SizeOf(typeof(CRYPTPROTECT_PROMPTSTRUCT))
            public int dwPromptFlags; // = 0
            public IntPtr hwndApp; // = IntPtr.Zero
            public string szPrompt; // = null
        }
    }


    internal class Win32Error
    ...{
        [Flags()]
            public enum FormatMessageFlags : int
        ...{
            FORMAT_MESSAGE_ALLOCATE_BUFFER = 0x0100,
            FORMAT_MESSAGE_IGNORE_INSERTS = 0x0200,
            FORMAT_MESSAGE_FROM_STRING = 0x0400,
            FORMAT_MESSAGE_FROM_HMODULE = 0x0800,
            FORMAT_MESSAGE_FROM_SYSTEM = 0x1000,
            FORMAT_MESSAGE_ARGUMENT_ARRAY = 0x2000,
            FORMAT_MESSAGE_MAX_WIDTH_MASK = 0xFF,
        }

        [DllImport("Kernel32.dll")]
        public static extern int FormatMessage(FormatMessageFlags flags, IntPtr source, int messageId, int languageId , 
            StringBuilder buffer, int size, IntPtr arguments);
    }
}